Project Summary/Abstract Aging is associated with an exponential increase in the incidence of cardiovascular diseases (CVD). Several mechanisms underlying age-associated cardiac changes in fly model and vertebrates have been proposed, for example, decreased cellular quality control, altered calcium handling, increased mitochondria damage, and the production of reactive oxygen species (ROS). Cellular quality control systems, like autophagy, are essential protective mechanisms for the maintenance of tissue homeostasis during cardiac aging. It is well-known that autophagy declines with age. However, the molecular basis for age-dependent dysregulation of autophagy and its contribution to cardiac homeostasis remain largely unknown. Our recent studies uncovered an exciting link between activin and mechanistic target of rapamycin complex 2 (mTORC2) in the regulation of autophagy and cardiac aging. We also noticed that two mTOR complexes (mTORC1 and mTORC2) seem to play distinct roles in autophagy regulation. Furthermore, through genetic screening we identified several activin- regulated systemic factors (e.g., Upd3, the fly homology of mammalian Interleukin 6, IL-6) that can mediate tissue-tissue communication and maintain cardiac homeostasis. In this proposal, we aim to dissect the distinct mechanisms by which activin signaling regulate autophagy and age- dependent cardiac dysfunctions through the interactions with two important pathways, mTORC2 and JAK-STAT. To achieve the overall objective, we propose two specific aims. Specific Aim 1: Determine how activin interacts with mTORC2 to regulate autophagy and cardiac aging; Specific Aim 2: Determine the role of activin and Upd3 in oenocyte-heart communication during aging. The mechanistic understanding of the tissue specificity and the underlying function of activin in cardiac aging will provide strong justification for its continued development as a novel target for potential therapeutic intervention.